Abstract
We report the structural and electrochemical characterization of the binuclear complex [μ-(C24H16N6){RuCl(C10H8N2)}2](PF6)2, which contains the bis-tridentate bridging ligand 2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine (tppz), the monodentate ligand Cl-, and the bidentate ligand 2,2'-bi-pyridine (bpy) {systematic name: μ-2,3,5,6-tetra-kis-(pyridin-2-yl)pyrazine-bis-[(2,2'-bi-pyridine)-chlorido-ru-thenium(II)] bis-(hexa-fluorido-phosphate)}. The complete [(bpy)(Cl)Ru(tppz)Ru(Cl)(bpy)]2+ dication is generated by crystallographic twofold symmetry; the tppz bridging ligand has a significantly twisted conformation, with an average angle of 42.4° between the mean planes of adjacent pyridyl rings. The metal-coordinated chloride ligands are in a trans configuration relative to each other across the {Ru(tppz)Ru} unit. The RuII ion exhibits a distorted octa-hedral geometry due to the restricted bite angle [160.6 (3)°] of the tppz ligand. For bpy, the bond lengths of the Ru-N bonds are 2.053 (8) and 2.090 (8) Å, with the shorter bond being opposite to Ru-Cl. For the tridentate tppz, the Ru-N distances involving the outer N atoms trans to each other are 2.069 (8) and 2.072 (9) Å, whereas the Ru-N bond involving the central N atom has the much shorter length of 1.939 (7) Å as a result of the geometric constraints and stronger π-acceptor ability of the pyrazine-centered bridge. The Ru-Cl distance is 2.407 (3) Å and the intra-molecular distance between Ru centers is 6.579 (4) Å. In the crystal, weak C-H⋯Cl and C-H⋯F inter-actions consolidate the packing.
Highlights
We report the structural and electrochemical characterization of the binuclear complex [-(C24H16N6){RuCl(C10H8N2)}2](PF6)2, which contains the bis-tridentate bridging ligand 2,3,5,6-tetrakis(pyridin-2-yl)pyrazine, the monodentate ligand ClÀ, and the bidentate ligand 2,20-bipyridine {systematic name: -2,3,5,6-tetrakis(pyridin-2-yl)pyrazine-bis[(2,20-bipyridine)chloridoruthenium(II)] bis(hexafluoridophosphate)}
The complete [(bpy)(Cl)Ru(tppz)Ru(Cl)(bpy)]2+ dication is generated by crystallographic twofold symmetry; the tppz bridging ligand has a significantly twisted conformation, with an average angle of 42.4 between the mean planes of adjacent pyridyl rings
The design and synthesis of electrochemically and photochemically active ruthenium(II)–polypyridine complexes have been of continued interest in the development of homogeneous electrocatalysis and photocatalysis toward watersplitting schemes for renewable energy applications (Yamazaki et al, 2010; Herrero et al, 2011; Jurss et al, 2012)
Summary
The design and synthesis of electrochemically and photochemically active ruthenium(II)–polypyridine complexes have been of continued interest in the development of homogeneous electrocatalysis and photocatalysis toward watersplitting schemes for renewable energy applications (Yamazaki et al, 2010; Herrero et al, 2011; Jurss et al, 2012). We introduced Ru dyads in which a lightharvesting Ru moiety (chromophore) and a multi-electron/ multi-proton redox-active Ru moiety (catalyst) were linked by back-to-back terpyridine (tpy–tpy) or tetrapyridylpyrazine (tppz) ligands to give modular light-driven oxidation catalysts with a varying extent of charge delocalization between the Ru centers (Chen et al, 2009, 2013). In such catalysts containing the {(tpy/tppz)Ru(bpy)(L)} moiety (L = H2O or ClÀ), the aqua species is typically formed by ligand substitution from its chloro precursor in water (Davidson et al, 2015b; Matias et al, 2016). E74, 1250–1253 research communications energy-transfer properties for potential applications in molecular (opto)electronic devices (Davidson et al, 2015a; Fantacci et al, 2004; Nagashima et al, 2014, 2016; Wadman et al, 2009)
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